Photographic developer compositions



United States Patent 01am 3,532,498 Patented Oct. 6, 1970 3,532,498 PHOTOGRAPHIC DEVELOPER COMPOSITIONS Ronald Cowell, Rayleigh, England, assignor to May & Baker Limited, Dagenham, Essex, England, a British company No Drawing. Filed Sept. 29, 1966, Ser. No. 583,099 Claims priority, application Great Britain, Oct. 7, 1965, 42,653/65 Int. Cl. G03c 5/30 U.S. Cl. 9666.1 3 Claims ABSTRACT OF THE DISCLOSURE The storage stability of photographic developer compositions is improved by providing a first concentrate containing 1-phenyl-3-pyrazolidone as developing agent which is in the form of a solution in a mixture of (a) butyrolactone or ethyl lactate with (b) formic acid or lactic acid and a second concentrate in the form of a solution of a polyhydric phenol as secondary developer, an alkali, an inorganic sulphite, and an antifoggant. The two concentrates are mixed prior to use and the mixture is diluted with water to produce a working strength developer solution having a pH of at least 9.5.

This invention relates to photographic developer compositions. It is known that photographic developer solutions containing the developing agent 1-phenyl-3-p-yrazolidone in aqueous solutions at a pH of 9.5 or above (i.e. at the pH value at which they are used) at temperatures above 20 C., deteriorate rapidly, as do also aqueous concentrates of 1-phenyl-3-pyrazolidone intended for incorporation into such developer solutions. This deterioration, particularly of aqueous 1-phenyl-3-pyrazolidone-containing concentrates, results in substantial storage problems under commercial conditions, in which it is often desirable to be able to store material for periods up to several years at temperatures which may range as high as 50 to 55 C. This problem is particularly acute in tropical countries.

A method of overcoming this problem has been indicated in British Pat. No. 948,294, in which it is specified that 1-phenyl-3-pyrazolidone can be stored in dissolved {form for indefinite periods and at temperatures up to 95 C. in solution in selected non-aqueous or substantially non-aqueous organic solvents, the solution being freely miscible with water at 20 C.30 C., and the solubility of the l-phenyl-3-pyrazolidone in the organic solvent being an amount corresponding to at least five grams of l-phenyl-3-pyrazolidone per one hundred millilitres of solvent. Such solutions may be used as storagestable concentrates which can be added to an aqueous bath containing the other ingredients normally present in a 1-phenyl-3-pyrazolidone-containig photographic developing composition, if necessary with further dilution with water, to give a developer solution ready for use. The aforementioned other ingredients are ordinarily a polyhydric phenol as secondary developer, an alkali, an inorganic sulphite, an autifoggant, and, optionally, a sequestering agent to prevent precipitation of metal ions in the working solution and a buffering agent. Optionally, one or more of these other ingredients may be dissolved in the 1-phenyl-3-pyrazolidone-containing concentrate. In practice, certain disadvantages are encountered 'in the use of photographic developer compositions in the form of two separate solutions of the type described above, i.e. one being a concentrate of 1-phenyl-3-pyrazolidone in a non-aqueous or substantially non-aqueous organic solvent and the other being an aqueous solution containing the other ingredients normally present in a l-phenyl-3-pyrazolidone-containing developer solution. When used as a concentrate, it is desirable to keep to a minimum the volume of the second, aqueous, solution which also normally has a pH value of 9.5 or above. Addition of the 1-phenyl-3-pyrazolidonecontaining solution to the second aqueous, highly alkaline, concentrate results in the precipitation of finely divided solid 1-phenyl-3-pyrazolidone which is difficult to redissolve and if allowed to remain in solid condition in the solution prevents the satisfactory development of photographic emulsions. In order to overcome this problem it is necessary either to dilute the second concentrate with further quantities of water before the first l-phenyl- 3-pyrazolidone-containing concentrate is added or to add further quantities of water to the two solutions immediately after they are mixed. The further quantities of water added are conveniently chosen to give working-strength developer solutions which have, under normal conditions, a limited effective life and may show substantial deterioration after periods as short as three days.

In practice, the two solutions are supplied in the form of two packs and frequently the quantity of workingstrength developer solution which is required is less than that obtained by the dilution to working-strength of the total contents of the packs. The operator is thus faced with the alternatives of (a) diluting the total contents of the packs, either immediately before or after the two concentrates are mixed, thus producing a quantity in excess of his immediate requirements of working-strength developer solution liable to rapid deterioration or (b) taking aliquot portions of solution from the two packs, an operation which frequently requires the very accurate measurement of small volumes of solution.

As a result of research and development, means have been found, and it is this which constitutes the essential feature of the present invention, by which the difficulties encountered with 1-phenyl-3 pyrazolidone-containing photographic developer compositions which comprise a first concentrate comprising a solution of l-phenyl-3- pyrazolidone in a non-aqueous or substantially nonaqueous organic solvent and a second concentrate comprising an aqueous solution of the other ingredients normally present in a 1-phenyl-3-pyrazolidone-containing developer composition, as hereinbefore described, may be overcome.

According to the present invention there are provided photographic developer compositions which take the form of two separate liquid concentrates, of which the first concentrate comprises a solution of l-phenyl-3- pyrazolidone dissolved in a substantially non-aqueous, i.e. containing not more than 5% w./v. of water, solvent in which the 1-phenyl-3-pyrazolidone is at least 5% w./v. soluble and preferably at least 10% W./v. soluble, at 20 C., which is a mixture of two -components, the first component being a water-miscible non-acidic organic solvent such as an ester or a cyclic ester i.e. lactone, and the second component being a water-miscible organic acid, and the second concentrate comprises a conventional developer concentrate of the 1-phenyl-3-pyrazolidone-containing type from which the 1-phenyl-3- pyrazolidone has been omitted, the compositions of the two concentrates being such that, on mixing with the second solution enough of the first solution to provide an appropriate proportion of 1-phenyl-3-pyrazolidone (e.g. between 0.1 gram and 2.0 grams per litre of lphenyl-3-pyrazolidone in working-strength developer solutions), the working-strength developer solution obtained by dilution of the mixture with further quantities of water has a pH of 9.5 or above. Preferably, the proportions by volume of the non-acidic organic component and the organic acid component of the solvent of the first solution are within the range 1:1 to 4:1 inclusive.

The solvent of the first solution must be readily and completely miscible with water at the temperature at which the two solutions are mixed, which will generally be within the range of 20 C. to 30 C. The two components of the solvent of the first solution must be substantially non-toxic, free from other serious hazards and suitable for use in developer compositions i.e. they must not affect the performance of, or cause precipitation of, the other components or be detrimental to the photographic material to be developed. More especially, according to a particularly preferred feature of the present invention, the non-acidic organic component is selected from the group consisting of ethyl lactate and butyrolactone and the organic acid component is selected from the group consisting of formic acid and lactic acid.

These concentrates are stable on prolonged storage, withstanding, for example, six months at 40 C. without significant loss of activity. They have the further advantage that crystallization does not normally occur on cooling to C.

With the photographic developer compositions of the present invention it is not necessary to dilute the developer concentrate obtained by mixing the two concentrates at the time the solutions are mixed. No finely divided solid 1-phenyl3-pyrazolidone is precipitated when the two concentrated solutions are mixed and the developer concentrate obtained by the use of the two solutions of the present invention is as stable as a corresponding l-phenyl-3- pyrazolidone-containing developer concentrate freshly prepared from its individual constituents. 'It is thus possible to mix the concentrates to give a standard developer concentrate which has satisfactory stability over the period of time normally required, i.e. up to two months at up to 30 C. temperatures, and which can be diluted in portions with Water to give working-strength developer solutions as required, thereby overcoming the difiiculties encountered with previously disclosed photographic developer compositions in the form of two solutions.

A further advantage of the photographic developer compositions of the present invention is that the presence in the first, l-phenyl-3-pyraZolidone-containing, concentrate of an organic acid exerts a stabilising effect on the 1-phenyl-3-pyrazolidone in respect of hydrolysis due to the presence of water, thereby enabling the first solution to be other than completely non-aqueous and to contain up to w./v. of water without serious deterioration being encountered on storage for periods up to at least six months at 40 C. at temperatures ranging up to 50-55 C.

The solutions used in the present invention will, in general, be of as small a volume as is practicable having regard to the fact that the ingredients, particularly the lphenyl-3-pyrazolidone, should not crystallize out on prolonged standing at 0 C. As the first concentrate, a solution of 1-phenyl-3-pyrazolidone in a 2:1 v./v. mixture of butyrolactone and lactic acid containing g. of l-phenn yl-3-pyrazolidone per 100 ml. of solution is particularly suitable.

The solution used in the second concentrate pack is, as already stated, a conventional l-phenyl-3-pyrazolidonecontaining developer from which the 1-phenyl-3-pyrazolidone has been omitted. Such developers ordinarily contain (besides l-phenyl-3-pyrazolidone) a polyhydric phenol as secondary developer, an alkali, an inorganic sulphite, an antifoggant, and, optionally a sequestering agent to prevent precipitation of metal ions in the working solutions and a buffering agent. The polyhydric phenol is generally hydroquinone, the alkali an alkali metal, for example sodium or potassium, hydroxide or carbonate, the inorganic sulphite an alkali metal, for example sodium or potassium, sulphite or metabisulphite, and the antifoggant an organic antifoggant, for example benzotriazole, or a source of bromide ions, for example an alkali metal, e.g. sodium or potassium, bromide. The sequestering agent which may be present is a sequestering agent for alkaline earth, particularly calcium, ions, for example N-hydroxyl ethyl-ethylenediamine N,N,N' triacetic acid trisodium salt or ethylenediaminetetraacetic acid tetrasodium salt. The buffering agent which may be present is usually a source of carbonate ions, for example an alkali metal, e.g. sodium or potassium, carbonate or bicarbonate, a source of borate ions, for example borax, an alkali metal, e.g. sodium or potassium, metaborate or boric acid, or a source of phosphate ions, for example an alkali metal, e.g. sodium or potassium, phosphate or polyphosphate. A typical formulation is given in the example below. The second concentrate should contain enough alkali to ensure that the pH of the mixture of the two concentrates, after dilution to working-strength with further quantities of water, is 9.5 or above. This is important as the activity of the developer is unsatisfactory below this.

The following example illustrates the invention:

EXAMPLE A two solution pack developer composition in accordance with the present invention is prepared as follows:

First solution pack 5 g. of 1-phenyl-3-pyrazolidone is added to ml. of lactic acid and butyrolactone added to give a total volume of ml.

Second solution pack A solution is prepared from: G. Sodium metabisulphite 680 Potassium hydroxide 553 Benzotriazole 5.5 N-Hydroxyethyl-ethylenediamine-N,N',N-triacetic acid trisodium salt 15.0

Borax 172 Hydroquinone 222 Potassium bromide 132 Water to 1 gallon.

The two solutions may be mixed together to give a photographic developer concentrate, portions, or the whole, of which may be diluted with water in the ratio of 1 part by volume of concentrate to 4 parts by volume of water to give a working-strength developer solution having a pH value of 10.6.

I claim:

1. Process for the production of a photographic developer which comprises the steps of (1) providing a first concentrate in the form of a solution of 1-phenyl-3-pyrazolidone in a mixture of (a) butyrolacetone or ethyl lactate with (b) formic acid or lactic acid and a second concentrate in the form of a solution of a polyhydric phenol as secondary developer, an alkali, an inorganic sulphite, and an antifoggant, (2) mixing the said concentrates, and (3) diluting the mixture with water to produce a solution having a pH of at least 9.5.

2. Process according to claim 1 wherein the proportions by volume of the said (a) butyrolactone or ethyl lactate and said (b) formic acid or lactic acid are in the range 1:1 to 4:1 inclusive.

3. Process according to claim 1 wherein the first concentrate is a solution of l-phenyl-3-pyrazolidone in a 2:1 v./v. mixture of butyrolactone and lactic acid containing 10 g. of 1-phenyl-3-pyrazolidone per ml. of solution.

References Cited UNITED STATES PATENTS 3,038,801 6/1962 Alletag 9666.l 3,178,284 4/1965 Oakley et al. 9666.l 3,369,898 2/1968 Baldoni et .al 9666.l

NORMAN G. TORCH'IN, Primary Examiner M. F. KELLEY, Assistant Examiner US. Cl. XJR. 

